Ablative ultrasonic-cryogenic apparatus

ABSTRACT

An ablative apparatus that can be used to treat atrial fibrillation and other cardiac arrhythmias by ablating cardiac tissue is disclosed. When the distal end of the apparatus reaches the tissue to be ablated, an ablation probe driven by a transducer is vibrated. Scratching the tissue with abrasive members, the vibrating ablation probe is capable of mechanically ablating tissues. This mechanical ablation may be utilized to penetrate epicardial fat, thereby exposing the underlying myocardium. The ablative apparatus may then be used subject the exposed myocardium to mechanical ablation, cryoablation, ultrasonic ablation, and/or any combination thereof.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.11/845,220, filed Aug. 27, 2006, now U.S. Pat. No. 7,540,870, which is acontinuation-in-part of abandoned U.S. patent application Ser. No.11/463,187, filed Aug. 8, 2006.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ablative apparatus that can be usedto treat atrial fibrillation and/or other cardiac arrhythmias byablating cardiac tissue.

2. Description of the Related Art

Accounting for one-third of the hospitalizations for cardiac arrhythmia,atrial fibrillation (AF) is the most common arrhythmia (abnormal beatingof the heart) encountered in clinical practice. AF is a specific type ofarrhythmia in which an abnormal beating of the heart originates in oneof the heart's two atrium. Increasing in prevalence, an estimated 2.2million Americans suffer from AF. Underlying one out of every sixstrokes, AF doubles the rate of morbidity compared to patients withnormal sinus rhythm. Further increasing the clinical severity, thepresence of AF leads to functional and structural changes in the atrialmyocardium (cells responsible for the beating of the heart) that favorsits maintenance. As such, AF is a serious disorder requiring medicalintervention.

Administering drugs that alter the electrical properties of atrialmyocardium has been effective in treating less severe cases of AF.However, such drugs often lead to the creation of pro-arrhythmicconditions thereby resulting in the treatment of one type of arrhythmiaonly to create another. Due to the increased risk of stroke, it isadvised that all patients with AF, despite the successfulness of drugtherapy, be prescribed warfarin or other anticoagulants to inhibit theformation of blood clots. Besides being difficult to dose, warfarin hasseveral complications associated with its long term use. Altering themetabolism of other drugs, warfarin is known to induce several adverseinteractions with other medications commonly prescribed to elderlypatients, who are at increased risk of developing AF.

AF originates in regions of myocardium contracting, or beating, out ofstep with the rest of the heart. Heart cells contract in response toelectrical stimulation. In a healthy heart, the electrical stimulationsignaling contraction originates from the sinus node (the heart'snatural pace maker) and spreads in an organized manner across the heart.In a heart plagued with AF, a region of myocardium elicits a mistimedcontraction, or heart beat, on its own or in response to an electricalsignal generated from somewhere other than the sinus node. Generating anelectrical signal, the mistimed contraction spreads across the heart,inducing contractions in neighboring regions of the heart. Inducing theformation of scar tissue on the heart by ablating, cutting, or otherwiseinjuring tissue in regions in which AF originates has been shown to beaffective in treating AF. The logic behind this treatment is toterminate AF by removing the heart cells responsible for its presence,while preserving healthy cells. Creating scar tissue barriers as toprevent the spread of electrical signals from mistimed contractions hasalso been shown to be effective in treating AF.

Successful surgical intervention eliminates the need for continuedwarfarin treatment in most patients. Initially surgical treatment wasreserved for patients undergoing additional cardiac surgery, such asvalve repair or replacement. The high success rate and efficacy ofsurgical intervention in the treatment of AF has spurred the developmentof cardiac catheters capable of therapeutically ablating cardiac tissuewithout the need for open chest or open heart surgery.

Heart surgery preformed by means of catheter involves, in it basicconception, the insertion of a catheter either into a patient's vein orchest cavity. The catheter is then advanced to the heart. When thecatheter is inserted into a patient's vein, the catheter is advancedinto one of the heart's four chambers. When the catheter in insertedinto a patient's chest, the catheter is advanced to the outer walls ofthe patient's heart. After the catheter reaches the patient's heart thesurgeon utilizes the catheter to ablate, damage or, kill cardiac tissue.The ideal catheter induced lesion is one that is created from theepicardium (outside) of the beating heart, is able to go throughepicardial fat, is performed rapidly over variable lengths, istransmural, causes no collateral injury, and can be applied at anydesired anatomic location. Ablating cardiac tissue by heating the tissueto 50 degrees Celsius has become the preferred means of inducinglesions. Cardiac catheters employing a variety of thermal ablativeenergy sources have been developed, none of which are capable ofinducing an ideal lesion.

Catheters utilizing radio frequency as an ablative energy source, thecurrent gold standard, are incapable of creating an ideal lesion. Inparticular, radio frequency catheters have a difficult time creatingablations through the epicardial fat surrounding the heart. Furthermore,inducing deep lesions with radio frequency is not possible withoutinflicting collateral damage from surface burning and steam popping.Steam popping is the phenomenon in which cells become heated to such apoint their internal fluids begin to boil, producing steam that burststhe cell. Simultaneously cooling the site of radio frequencyadministration reduces the incidence of surface burns but does notreduce the risk of steam popping. In an effort to overcome theshortcomings of radio frequency induced lesions, catheters employingnovel energy sources have been developed.

In hopes that microwaves would provide sufficiently deep lesions,catheters employing microwaves as an ablative energy source have beendeveloped. Because the penetration of microwaves into tissue has a steepexponential decline, it has been found necessary to bring the catheterinto close contact with the tissue in order to induce deep lesions.Furthermore, fat continues to be a significant barrier.

Lasers have also been applied as an ablative energy source withincatheters. Although high powered lasers carry a high risk of craterformation at the site of application, low energy lasers produce lesionswith a depth related to the duration of application.

Capable of penetrating fat and inducing fasts lesion at specific depthswhen focused, high intensity ultrasound has been predicted to be anadvantageous source of ablative energy in catheters.

An alternative to ablation by heating is the practice of ablating tissueby freezing. Severe cold, also know cryogenic energy, as an ablativeenergy source has the advantages of avoiding clot formation. Anotheradvantage of catheters employing cryogenic energy is the ability totemporary paralyze regions of myocardium tissue as to test the benefitof a planned lesion. When a region of tissue is paralyzed by freezing itcan no longer initiate an arrhythmia. If paralyzing a region of theheart completely or partial restores a normal heart beat, the surgeonknows she has her catheter aimed at the right spot.

SUMMARY OF THE INVENTION

An ablative apparatus that can be used to ablate cardiac tissue isdisclosed. The ablative apparatus comprises an ablation probe, atransducer capable of ultrasonically driving the ablation probe incontact with the proximal end of the ablation probe, a guide wiresecured at one end to the transducer and/or ablation probe, electricalleads running along the guide wire and connected to electrodes capableof exposing piezo ceramic discs within the transducer to an alternatingvoltage, a catheter encasing the ablation probe, transducer, and atleast a portion of the guide wire, and a handle secured to the end ofthe guide wire opposite the transducer. Preferably, the catheter iscomposed of a biologically compatible polymer.

The ablation probe located at the distal end of the catheter system maycomprise a proximal surface, a distal surface opposite the proximalsurface, at least one radial surface extending between the proximalsurface and the distal surface, and at least one abrasive member on atleast one surface other than the proximal surface. As the distal end ofthe ablative apparatus is advanced towards the heart, the ablation probemay be contained within a pocket at the distal end of the catheter. Whenthe distal end of the catheter reaches the tissue to be ablated, theablation probe may be removed from the pocket, as to expose the abrasivemember(s). When the transducer in contact with the proximal surface ofthe ablation probe is activated by supplying it with an electricalcurrent, the ablation probe becomes driven by ultrasonic energygenerated by the transducer and begins to vibrate. As the ablation probevibrates, the abrasive members on the ablation probe scratch tissueswith which the members come in contact, as to create an abrasion in thetissues. Physically inducing an abrasion within a tissue, the vibratingablation probe is capable of mechanically ablating tissues. When theablation probe is advanced to the heart, mechanical ablation may beutilized to penetrate epicardial fat, thereby exposing the underlyingmyocardium. The exposed myocardium may then be subjected to mechanicalablation, cryoablation, ultrasonic ablation, and/or any combinationthereof.

Flowing a cryogenic material through the catheter, as to delivercryogenic energy to the ablation probe, to a region of the catheter inclose proximity to the ablation probe, and/or to another region of thecatheter, may enable cryoablation. Lumens running substantially thelength of the catheter and joined by a junction may enable a cryogenicmaterial to flow through the catheter. Such lumens may comprise acryogenic intake lumen originating at the proximal end of the catheterand running substantially the length of the catheter, through which acryogenic material flows from the proximal end of the catheter towardsits distal end. Likewise, a cryogenic exhaust lumen runningsubstantially the length of the catheter and substantially parallel tothe cryogenic intake lumen and terminating at the proximal end of thecatheter may permit a cryogenic material to flow towards the proximalend of the catheter. A junction at the distal end of the intake lumenand exhaust lumen connecting the lumens may permit a cryogenic materialto be exchanged between the lumens. The cryogenic material may beprevented from exiting the catheter by a partition distal to thejunction isolating the intake lumen and exhaust lumen from the remainingdistal portions of the catheter. Thus, a cryogenic material may beflowed through the catheter by first flowing through an intake lumen andtowards the distal end of the catheter. The cryogenic material thenexits the intake lumen and enters the exhaust lumen at a junctionconnecting the lumens. Completing its flow through the catheter, thecryogenic material then flows through the exhaust lumen and back towardsthe proximal end of the catheter.

Cryogenic ablation may also be enabled by flowing a cryogenic materialthrough the guide wire. As with the catheter, lumens runningsubstantially the length of the guide wire and joined by a junction mayenable a cryogenic material to flow through the guide wire. Such lumensmay comprise cryogenic intake lumen originating at the proximal end ofthe guide wire and running substantially the length of the wire, throughwhich a cryogenic material flows from the proximal end of the guide wiretowards its distal end. Likewise, a cryogenic exhaust lumen runningsubstantially the length of the wire and substantially parallel to thecryogenic intake lumen and terminating at the proximal end of the wiremay permit a cryogenic material to flow towards the proximal end of thewire. A junction at the distal end of the intake lumen and exhaust lumenconnecting the lumens may permit a cryogenic material to be exchangedbetween the lumens. The junction connecting the lumens may comprise achamber internal to the ablation probe into which the intake lumen andexhaust lumen open. Thus, a cryogenic material may be flowed through theguide wire by first flowing through an intake lumen and towards thedistal end of the wire. The cryogenic material then exits the intakelumen and enters the exhaust lumen at a junction connecting the lumens.Completing its flow through the wire, the cryogenic material then flowsthrough the exhaust lumen and back towards the distal end of thecatheter.

Regardless of whether a cryogenic material is flowed through thecatheter or guide wire, the ablative apparatus enables the surgicaltreatment of cardiac arrhythmias by providing a means to mechanically,ultrasonically, and/or cryogenically ablate myocardial tissue. As such,a surgeon utilizing the disclosed ablative apparatus will be able toselect the appropriate ablative means or combination of ablative meansbest suited for the patient's particular pathology and the type oflesion the surgeon wishes to induce. Driving the ablation probe withultrasound energy generated by the transducer enables a surgeon toquickly induce surface abrasions of various depths by adjusting thepulse frequency and duration of the driving ultrasound. This may proveadvantageous when the surgeon wishes to induce a lesion at a specificlocation with minimal collateral injury, such as during AV nodalmodification.

Combining ultrasonic energy with cryogenic energy, the ablativeapparatus may enable the surgeon to cryoablate tissue without theablation probe adhering to the tissue being ablated. As such, thesurgeon may be able to easily move the probe during ablation. Theablation probe may be moved during the induction of a lesion byincluding control means for steering and/or rotating the ablation probewithin the handle. The probe's mobility during cryoablation could allowthe surgeon to create linear lesions in cardiac tissue or isolatinglesions in vessel walls. Thus, by combining ultrasonic and cryogenicenergy the ablative apparatus may give the surgeon greater control overthe lesion induced. Furthermore, it has been hypothesized that theadministration of low frequency ultrasound and cryoablation induces therelease of several healing factors from the targeted tissue. Therefore,ultrasonically vibrating the ablation probe during cryoablation mayimprove mobility of the ablation probe and possibly induce healing.

Alternatively or in combination, dually administering ultrasonic energyand cryogenic energy may protect surface tissue during theadministration of a deep lesion, thereby limiting collateral damage.During the cryogenic induction of a deep lesion, the co-administrationof ultrasonic energy will warm the surface tissue preventing it fromfreezing. Likewise, administering cryogenic energy during the inductionof a deep lesion with ultrasonic energy will cool surface tissue therebyprotecting it from ablative cavitation, possibly by reducing molecularmovement.

In the alternative or in combination, the ablative apparatus may alsoenable the surgeon to deliver various drugs and/or other pharmacologicalcompounds to the location of the lesion and/or other locations.Combining drug delivery with the application of ultrasound energy mayassist drug delivery and drug penetration into the targeted tissue.Delivering an antithrombolytic during the induction of a lesion mayreduce the likelihood of clot formation, especially during mechanicalablation. The surgeon may also choose to expedite healing by deliveringvarious healing and/or growth factors to the site of the lesion.

Drug delivery may be accomplished by coating the ablation probe with adrug or other pharmacological compound. When so coated, driving theablation probe with ultrasonic energy may liberate the drug coating fromthe probe and embed it within the targeted tissue. In the alternative orin combination, the catheter may contain a drug lumen and/or reservoirpermitting the administration of a drug to internal locations of thepatient's body.

BRIEF DESCRIPTION OF THE DRAWINGS

The ablative apparatus will be shown and described with reference to thedrawings of preferred embodiments and clearly understood in detail.

FIG. 1 depicts a possible embodiment of the ablative apparatus.

FIG. 2 depicts cross-sectional views of the proximal end of theembodiment of the ablative apparatus depicted in FIG. 1.

FIG. 3 depicts an alternative embodiment of the ablative apparatus.

FIG. 4 depicts cross-sectional views of the proximal end of theembodiment of the ablative apparatus depicted in FIG. 3.

FIG. 5 depicts various ablation probes each comprising a distal surface,a proximal surface opposite the distal surface, a radial surfaceextending between the proximal surface and the distal surface, andabrasive members on a surface other than the proximal surface.

FIG. 6 depicts different piezo ceramic disc configurations that may beincluded within the transducer utilized to drive the ablation probe.

DETAILED DESCRIPTION OF THE INVENTION

Disclosed is an ablative apparatus that may be used to treat atrialfibrillation and other arrhythmias. Preferred embodiments of theablative apparatus are illustrated in the figures and described indetail below.

FIG. 1 depicts a possible embodiment of the ablative apparatus. Theablative apparatus comprises an ablation probe 101, a transducer 102capable of capable of ultrasonically driving the ablation probe 101 incontact with the proximal surface 103 of ablation probe 101, a guidewire 104 secured at one end to transducer 102, electrical leads 105running along guide wire 104 and connected to electrodes 113 capable ofexposing piezo ceramic disc 112 within transducer 102 to an alternatingvoltage, a catheter 106 encasing ablation probe 101, transducer 102, andat least a portion of guide wire 104, and a handle 107 secured to theend of guide wire 104 opposite transducer 102. Preferably, catheter 106is composed of a biologically compatible polymer. Handle 107 may containcontrol means 108 for steering and/or rotating ablation probe 101.Exemplar control means have been described in U.S. Pat. Nos. 4,582,181and 4,960,134, the teachings of which are incorporated herein byreference. In addition to housing control means, handle 107 may providea means of rotating ablation probe 101. When rotated, ablation probe 101moves in a circular motion similar to the manner in which the hands ofclock move about its face. Rotation of ablation probe 101 can beaccomplished by the surgeon turning handle 107 with his wrist as if hewere using a screw driver. Extending from handle 107, through catheter106, to transducer 102, guide wire 104 provides rigidity to catheter106. Guide wire 104 may also carry electrical leads 105 down catheter106 to transducer 101. Transmitting an electrical current generated bygenerator 127 to transducer 102, electrical leads 105 energizetransducer 102 as to drive ablation probe 101.

In keeping with FIG. 1, a portion of the distal end 122 of catheter 106has been cut away as to expose ablation probe 101 and transducer 102.Ablation probe 101 comprises a distal surface 109, a proximal surface103 opposite the distal surface 109, at least one radial surface 110extending between distal surface 109 and proximal surface 103, andabrasive members 111 on radial surface 110. Transducer 102, in contactwith the proximal surface 103 of ablation probe 101, comprises a stackof piezo ceramic discs 112 arranged in a manner similar to that of aroll of coins. Running from generator 127 to electrodes 113, electricalleads 105 carry a current to electrodes 113 as to expose piezo ceramicdiscs 112 to an alternating voltage. So energizing transducer 102induces the expansion and contraction of piezo ceramic discs 112, as todrive ablation probe 101. Expanding and contracting, piezo ceramic discs112 apply ultrasonic energy to ablation probe 101. Applying ultrasonicenergy to probe 101 may induce a vibrating or oscillating movement ofprobe 101. As ablation probe 101 moves, abrasive members 111 scratchtissues with which the members 111 come in contact, as to create anabrasion in the tissue. Back drive 114, located at the proximal end oftransducer 102, stabilizes ablation probe 101 when it is driven byultrasound energy generated by transducer 102.

Continuing with FIG. 1, catheter 106, encasing ablation probe 101,transducer 102, and a portion of guide wire 104, contains a pocket 115at its distal end 122 encasing ablation probe 101. Encasing ablationprobe 101 within pocket 115 may enable the distal end of the ablativeapparatus to be advanced towards the tissue to be ablated withoutabrasive members 111 damaging tissue. When the distal end 122 of thecatheter 106 reaches the tissue to be ablated, ablation probe 101 may beremoved from pocket 115, as to expose abrasive members 111, by firmlypulling catheter 106 towards handle 107. As to facilitate thepenetration of the sealed tip 116 at the distal end of pocket 115 byablation probe 101, sealed tip 116 may contain single or multiple slits117. Slit(s) 117 may completely or partially penetrate sealed tip 116.Conversely, firmly pulling handle 107 away from the patient whilecatheter 106 is held stationary returns ablation probe 101 to the insideof pocket 115. Advancing the ablative apparatus into and through thepatient's body with ablation probe 101 retracted within pocket 115protects the patient's internal tissues from damage by abrasive members111. When ablation probe 101 has been advanced to the desired location,the surgeon may retract catheter 106, exposing ablation probe 101. Thesurgeon may then mechanically ablate the target tissue by drivingablation probe 101 with ultrasound energy generated by transducer 102.Alternatively, the surgeon may not expose ablation probe 101, but ratherinduce a lesion with low frequency ultrasound energy and/or cryogenicenergy.

In keeping with FIG. 1, flowing a cryogenic material through catheter106, as to deliver cryogenic energy to ablation probe 101, to a regionof catheter 106 in close proximity to ablation probe 101, and/or toanother region of catheter 106, may enable cryoablation. A cryogenicmaterial may be delivered to catheter 106 from a cryogenic storage andretrieval unit 118 in fluid communication with cryogenic intake lumen119 via cryogenic feed tubing 120, attached to the proximal end intakelumen 119. Originating at the proximal end 121 of catheter 106 andrunning substantially the length of catheter 106, cryogenic intake lumen119 permits a cryogenic material entering catheter 106 from storage andretrieval unit 118 to flow towards the distal end 122 of catheter 106.After reaching the distal end of intake lumen 119, the cryogenicmaterial flows through a junction connecting intake lumen 119 withexhaust lumen 123 located at the distal end of the intake lumen 119 andexhaust lumen 123. The specific junction depicted in FIG. 1 comprises aport 124 between intake lumen 119 and exhaust lumen 123. Runningsubstantially the length of catheter 106, substantially parallel tointake lumen 119, and terminating at the proximal end 121 of catheter106, exhaust lumen 123 permits the cryogenic material to flow towardsproximal end 121 of catheter 106. After reaching the proximal end 121 ofcatheter 106, the cryogenic material is returned to storage andretrieval unit 118 via cryogenic exhaust tubing 125 attached to theproximal end exhaust lumen 123, which is in fluid communication withstorage and retrieval unit 118 and exhaust lumen 123. Cryogenic storageand retrieval may alternatively be accomplished by the simultaneous useof separate storage and retrieval units. The storage and retrieval unitmay also permit the recycling of the employed cryogenic material as toreduce operation costs.

As to prevent the cryogenic material from entering pocket 115 and/orexiting catheter 106, a partition 126 distal to port 124 isolates intakelumen 119 and exhaust lumen 123 from pocket 115.

In order to prevent catheter 106 from becoming rigid and inflexible ascryogenic material flows through it, catheter 106, or portion thereof,may be wrapped with a wire conducting an electrical current. Theresistance in the wire to the flow of electricity may generate heat thatwarms catheter 106, thereby keeping it flexible. Alternatively, thewarming wire may be wrapped around guide wire 104.

Disclosed in U.S. patent application Ser. No. 11/454,018, entitledMethod and Apparatus for Treating Vascular Obstructions, and filed Jul.15, 2006, are exemplar configurations of catheters that may be used inthe alternative to catheter 106. The teachings of U.S. patentapplication Ser. No. 11/454,018 are hereby incorporated by reference.

FIG. 2 depicts cross-sectional views of the proximal end of theembodiment of the ablative apparatus depicted in FIG. 1. FIG. 2A depictsa cross-sectional view of the embodiment of the apparatus depicted inFIG. 1 with ablation probe 101 extended from pocket 115. FIG. 2B depictsa cross-sectional view of the embodiment of the apparatus depicted inFIG. 1 with ablation probe 101 retracted into pocket 115. As previouslystated in the discussion of FIG. 1, catheter 106 comprises a cryogenicintake lumen 119 and an exhaust lumen 123 (obscured in the present viewby intake lumen 119) connected by ports 124. The flow of a cryogenicmaterial from the proximal end 121 of catheter 106 towards the distalend 122 of catheter 106 through intake lumen 119, across ports 124, andthen back towards the proximal end 121 through exhaust lumen 123 coolspocket 115. Flowing adjacent to or in close proximity to ablation probe101 and/or transducer 102, the cryogenic material flowing throughcatheter 106 may also cool ablation probe 101 and/or transducer 102. Itshould be appreciated that in the alternative to the ports depicted inFIGS. 1 and 2, the junction between the intake lumen 119 and exhaustlumen 123 may comprise a chamber.

FIG. 3 depicts an alternative embodiment of the ablative apparatus. Thedepicted embodiment of the ablative apparatus comprises an ablationprobe 301, a transducer 302 capable of ultrasonically driving theablation probe 301 in contact with the proximal surface 303 of ablationprobe 301, a guide wire 304 secured at one end to ablation probe 301and/or transducer 302, electrical leads 305 running along guide wire 304and connected to electrodes 313 capable exposing piezo ceramic disc 312within transducer 302 to an alternating voltage, a catheter 306 encasingablation probe 301, transducer 302, and at least a portion of guide wire304, and a handle 307 secured to the end of guide wire 304 oppositeablation probe 301. Handle 307 may contain control means 308 forsteering and/or rotating ablation probe 301. Exemplar control means havebeen described in U.S. Pat. Nos. 4,582,181 and 4,960,134, the teachingsof which were previously incorporated herein by reference. In additionto housing control means, handle 308 may provide a means of rotatingablation probe 301. As with the embodiment depicted in FIG. 1, therotation of ablation probe 301 can be accomplished by the surgeonturning handle 307 with his wrist as if he were using a screw driver.Extending from handle 307, through catheter 306, to ablation probe 301,guide wire 304 provides rigidity to catheter 306. Guide wire 304 mayalso carry electrical leads 305 down catheter 306 to transducer 302.Transmitting an electrical current generated by generator 327 totransducer 302, electrical leads 305 energize transducer 302 as to driveablation probe 301.

In keeping with FIG. 3, a portion of the distal end 322 of catheter 306has been cut away as to expose ablation probe 301 and transducer 302.Ablation probe 301 comprises a distal surface 309, a proximal surface303 opposite the distal surface 309, at least one radial surface 310extending between distal surface 309 and proximal surface 303, andabrasive members 311 on radial surface 310. Transducer 302, in contactwith the proximal surface 303 of ablation probe 301 and encircling guidewire 304, comprises a stack of piezo ceramic discs 312 arranged in amanner similar to that of a roll of coins. Running from generator 327 toelectrodes 313, electrical leads 305 carry a current to electrodes 313as to expose piezo ceramic discs 312 to an alternating voltage. Soenergizing transducer 302 induces the expansion and contraction of piezoceramic discs 312, as to drive ablation probe 301. Expanding andcontracting, piezo ceramic discs 312 apply ultrasonic energy to ablationprobe 301. Applying ultrasonic energy to probe 301 may induce avibrating or oscillating movement of probe 301. As ablation probe 301moves, abrasive members 311 scratch tissues with which the members 311come in contact, as to create an abrasion in the tissue. Back drive 314,located at the proximal end of transducer 302, stabilizes ablation probe301 when it is driven by ultrasound energy generated by transducer 302.

Continuing with FIG. 3, catheter 306, encasing ablation probe 301,transducer 302, and a portion of guide wire 304, contains a pocket 315at its distal end 322 encasing ablation probe 301. Encasing ablationprobe 301 within pocket 315 may enable the distal end of the ablativeapparatus to be advanced towards the tissue to be ablated withoutabrasive members 311 damaging tissue. When the distal end 322 of thecatheter 306 reaches the tissue to be ablated, ablation probe 301 may beremoved from pocket 315, as to expose abrasive members 311, by firmlypulling catheter 306 towards handle 307. As to facilitate thepenetration of the sealed tip 316 at the distal end of pocket 315 byablation probe 301, sealed tip 316 may contain single or multiple slits317. Slit(s) 317 may completely or partially penetrate sealed tip 316.Conversely, firmly pulling handle 307 away from the patient whileholding catheter 306 stationary returns ablation probe 301 to the insideof pocket 315. Advancing the ablative apparatus into and through thepatient's body with ablation probe 301 retracted within pocket 315protects the patient's internal tissues from damage by abrasive members311. When ablation probe 301 has been advanced to the desired location,the surgeon may retract catheter 306, exposing ablation probe 301. Thesurgeon may then mechanically ablate the target tissue by drivingablation probe 301 with ultrasound energy generated by transducer 302.Alternatively, the surgeon may not expose ablation probe 301, but ratherinduce a lesion with low frequency ultrasound energy and/or cryogenicenergy.

In keeping with FIG. 3, flowing a cryogenic material through guide wire304, as to deliver cryogenic energy to ablation probe 301, may enablecryoablation. A cryogenic material may be delivered to guide wire 304from a cryogenic storage and retrieval unit 318 in fluid communicationwith cryogenic intake lumen 319 via cryogenic feed tubing 320, attachedto the proximal end intake lumen 319. Originating at the proximal end321 of guide wire 304 and running substantially the length of guide wire304, cryogenic intake lumen 319 permits a cryogenic material enteringguide wire 304 from storage and retrieval unit 318 to flow towards thedistal end 326 of guide wire 304. After reaching the distal end ofintake lumen 319, the cryogenic material flows through a junctionconnecting intake lumen 319 with exhaust lumen 323 at the distal end ofthe intake lumen 319 and exhaust lumen 323. The specific junctiondepicted in FIG. 3 comprises an expansion chamber 324 within ablationprobe 301 into which intake lumen 319 and exhaust lumen 323 open.Running substantially the length of guide wire 304, substantiallyparallel to intake lumen 319, and terminating at the proximal end 321 ofguide wire 304, exhaust lumen 323 permits the cryogenic material to flowtowards proximal end 321 of guide wire 304. After reaching the proximalend 321 of guide wire 304, the cryogenic material is returned to storageand retrieval unit 318 via cryogenic exhaust tubing 325 attached to theproximal end exhaust lumen 323, which is in fluid communication withstorage and retrieval unit 318 and exhaust lumen 323. Cryogenic storageand retrieval may alternatively be accomplished by the simultaneous useof separate storage and retrieval units. The storage and retrieval unitmay also permit the recycling of the employed cryogenic material as toreduce operation costs.

In order to prevent catheter 306 from becoming rigid and inflexible ascryogenic material flows through guide wire 304, catheter 306, orportion thereof, may be wrapped with a wire conducting an electricalcurrent. The resistance in the wire to the flow of electricity maygenerate heat that warms catheter 306, thereby keeping it flexible.Alternatively, the warming wire may be wrapped around guide wire 304.

FIG. 4 depicts cross-sectional views of the proximal end of theembodiment of the ablative apparatus depicted in FIG. 3. FIG. 4A depictsa cross-sectional view of the embodiment of the apparatus depicted inFIG. 3 with ablation probe 301 extended from pocket 315. FIG. 4B depictsa cross-sectional view of the embodiment of the apparatus depicted inFIG. 3 with ablation probe 301 retracted into pocket 315. As previouslystated in the discussion of FIG. 3, guide wire 304 comprises a cryogenicintake lumen 319 and an exhaust lumen 323 connected by expansion chamber324. The flow of a cryogenic material from the proximal end 321 of guidewire 304 towards the distal end 326 of guide wire 304 through intakelumen 319, across the junction formed by expansion chamber 324, and thenback towards the proximal end 321 through exhaust lumen 323 coolsablation probe 301. Expansion chamber 324 may be located within ablationprobe 301, as depicted in FIGS. 3 and 4. Alternatively, expansionchamber 324 may be located within transducer 302 and could, but neednot, extend into ablation probe 301. It should be appreciated that inthe alternative to the expansion chamber depicted in FIGS. 3 and 4, thejunction between the intake lumen 319 and exhaust lumen 323 may compriseone or a series of ports connecting intake lumen 319 with exhaust lumen323.

Incorporating threading on a portion of the ablation probe and/ortransducer along with corresponding threading on the internal surface ofthe catheter's pocket may facilitate a smooth deployment of the ablationprobe from the catheter's pocket. In such an embodiment, the surgeonwould advance the ablation probe from the pocket by rotating the guidewire and attached ablation probe. Rotating the guide wire in theopposite direction would retract the ablation probe back into thepocket.

The ablation probe of the ablative apparatus may contain one or multipleabrasive members attached to its proximal and/or radial surfaces.Furthermore, the abrasive members may be constructed in variousconfigurations, as depicted in FIG. 5.

FIG. 5 depicts various ablation probes each comprising a distal surface,a proximal surface opposite the distal surface, and a radial surfaceextending between the proximal surface and the distal surface, andabrasive members on a surface other than the proximal surface. Theablation probe 501, depicted in FIG. 5A, contains an abrasive membercomprising a thin band 502 attached to radial surface 503 and spiralingaround ablation probe 501 similar to the threads of a screw.Alternatively, the ablation probe 504, as depicted in FIG. 5B, maycontain abrasive members comprising a thin band 505 attached to radialsurface 506 and encircling ablation probe 504. As indicated by ablationprobe 507, depicted in FIG. 5C, it also possible for the abrasive memberto comprise small particle 508, conceptually similar to a grain of griton a piece of sand paper, attached to the proximal surface 509 and/orradial surface 510 of ablation probe 507. It is also possible, asindicated by ablation probe 511, depicted in FIG. 5D, for the abrasivemember to comprise a protrusion 512 extending from a surface of theablation probe 511 other than proximal surface 513. It should beappreciated that the ablation probes depicted in FIG. 5 may beconstructed by attaching or affixing the depicted abrasive members totheir proximal and/or radial surfaces. Alternatively, the ablationprobes depicted in FIG. 5 may be constructed such that the abrasivemembers are extensions of or integral with the ablation probes.

FIG. 6 depicts different piezo ceramic disc configurations that may beincluded within the transducer utilized to drive the ablation probe. Thetransducer may be comprised of a single piezo ceramic disc.Alternatively, the transducer may contain a collection of piezo ceramicdiscs as depicted in FIG. 6. For instance, the transducer may contain acollection cylindrical piezo ceramic discs 601 stacked upon one anotherin a manner resembling a roll of coins, as depicted in FIG. 6A. Such anarrangement may impart an axial or longitudinal displacement upon thedriven ablation probe when the transducer is energized. Alternatively,the transducer may contain a pair of half cylindrical piezo ceramicdiscs 602 combined to form a cylinder, as depicted in FIG. 6C. Such anarrangement may impart a circumferential displacement upon the drivenablation probe when the transducer is energized. The transducer may alsocontain a combination of cylindrical piezo ceramic discs 601 and halfcylindrical piezo ceramic discs 602, as depicted in FIG. 6B. Such acombination arrangement may impart an axial and circumferentialdisplacement upon the driven ablation probe when the transducer isenergized.

The ultrasound transducer responsible for driving the ablation probeneed not be in direct contact with the ablation probe. Instead, thetransducer may be in communication with the guide wire attached to theablation probe, driving the ablation probe through said communication.In such an embodiment, the transducer may be located anywhere within theablative apparatus, including, but not limited to, the handle. Thetransducer may also be located elsewhere within the ablative apparatus,provided the transducer is in direct or indirect communication with theablation probe.

The transducer utilized in the ablative apparatus should be capable ofinducing the ablation probe to vibrate at a frequency betweenapproximately 20 kHz and approximately 20 MHz. The recommended frequencyof vibration is approximately 30 kHz to approximately 40 kHz. Thetransducer should also be capable of driving the transducer withultrasonic energy having an intensity of at least approximately 0.1Watts per centimeter squared.

Pulse duration and treatment time are dependent upon the depth and typeof lesion the surgeon wishes to induce. Pulsing the ultrasound energydriving the transducer by repeatedly turning the transducer on and offgives the surgeon control over lesion depth. Incorporating an ultrasoundcontroller may permit the surgeon to control, regulate, or adjust, thepulse duration and pulse frequency of the driving ultrasound. Adjustingthe pulse frequency and duration enables the surgeon to control thedepth of the lesion inflicted by the ablation probe.

When the ablation probe has been advanced to the desired lesionlocation, the surgeon may retract the catheter as to expose the ablationprobe's abrasive member(s). The surgeon may then mechanical induce anabrasion by driving the ablation probe with ultrasound energy generatedby the transducer. Alternatively, the surgeon may not expose theablation probe's abrasive members but rather activate the flow ofcryogenic material through the ablative apparatus as to induce a lesionby means of cryoablation. If the surgeon wishes to induce a continuouslesion across a segment of cardiac tissue, the surgeon may activate thetransducer as to prevent cryoadhesion of the catheter's distal end tothe target tissue. Activating the transducer during cryoablation enablesthe surgeon to warm surface tissue at the site of ablation, therebyprotecting surface tissue from ablation or injury. Likewise, activatingthe flow of cryogenic material through the apparatus whileultrasonically inducing a lesion enables the surgeon to cool surfacetissue at the site of the ablation, thereby protecting it from ablationor injury.

Incorporating a mapping electrode placed at or near the distal end ofthe ablative apparatus may assist the surgeon in locating specific sitesof arrhythmia. Alternatively, the mapping electrode may be located at orattached to the ablation probe. A mapping electrode may enable thesurgeon to detect the electrical activity of the cells near theelectrode. The surgeon could use the detected electrical activity todetermine if the cells near the electrode are contributing to thearrhythmia. Furthermore, the surgeon may administer cryogenic energy toa region of myocardium suspected to be contributing to the patient'sarrhythmia as to paralyze the tissue. If paralyzing the tissuecompletely or partially corrects the arrhythmia, the surgeon may thenablate the tissue with the ablation probe.

Incorporating a temperature sensor placed at or near the distal end ofthe ablative apparatus may enable the surgeon to monitor the temperatureat the site of the ablation. Alternatively, the sensor may be locatednear or attached to the ablation probe. Monitoring the temperature nearor at the site of the ablation with the temperature sensor may assistthe surgeon in avoiding burning and/or inflicting other undesirabledamage or injury. When the temperature of the tissue being ablatedreaches or approaches an undesirable level, the surgeon could stop theablation and allow the tissue to return to a safer temperature. Thesurgeon may also adjust the ultrasound parameters as to slow the changein temperature. If the ablative procedure being performed involves theadministration of cryogenic energy, the surgeon may adjust the flow ofthe cryogenic material through the catheter system as to slow the changein temperature.

The ablative apparatus may also contain a drug lumen through which adrug solution or other fluid or composition may be introduced into thepatient's body. Ultrasonically driving the ablation probe, whilesimultaneously delivering drug through the apparatus by way of the druglumen, may be utilized by the surgeon to facilitate the release of thedrug from the apparatus, as well as the penetration of the drug intotargeted tissue.

The ablative apparatus may also contain a drug reservoir at its distalend. The drug reservoir may surround the ablation probe. Alternatively,the drug reservoir may be located distal to the ablation probe. Whenlocated distal to the ablation probe, the drug reservoir may containslits at its base. The slits may completely or partially penetrate thebase of the drug reservoir. Retracting the catheter may then cause theablation probe to penetrate the base of the drug reservoir andeventually the distal end of the reservoir. Traveling through the drugreservoir, the ablation probe may be coated with a drug. Suspending thedrug within a viscous or gel solution may offer better coating of theablation probe as it travels through the drug reservoir. Ultrasonicallydriving the ablation probe will cause the drug solution clinging to theablation probe to be liberated from the ablation probe and embedded inthe tissue at and surrounding the site of the lesion. Similarly,ultrasonically driving the ablation probe while the probe is retractedmay cause the release of drug from the drug reservoir.

Alternatively, drug delivery during the induction of lesions may beaccomplished by first coating the ablation probe with a pharmacologicalcompound. As in the above mention embodiment, ultrasonically driving theablation probe will liberate the drug compound coating; dispersing itinto the targeted tissue.

It should be appreciated that the term “cryoadhesion,” as used herein,refers to the freezing of a cooled and/or cold object to tissues of thebody.

It should be appreciated that the term “biologically compatiblepolymer,” as used herein, refers to polymers, or plastics, that will notnormally irritate or harm the body. Such polymers are familiar to thoseskilled in the art.

It should be appreciate that term “piezo ceramic disc,” as used herein,refers to an element composed of a ceramic material that expands andcontracts when exposed to an alternating voltage. Such ceramics are wellknown to those skilled in the art.

It should be appreciated that “energizing the transducer,” as usedherein, refers to inducing the contraction and expansion of piezoceramic discs within the transducer by exposing the discs to analternating voltage, as to induce the generation of ultrasonic energy.

It should be appreciated that the term “ultrasonically driven,” as usedherein, refers to causing the ablation probe to move by applying to theprobe ultrasonic energy generated by a transducer in direct or indirectcontract with the probe. The induced movement of the probe may includevibrating, oscillating, and/or other manners of motion.

It should be appreciated that the term “pulse duration,” as used herein,refers to the length of time the transducer is generating ultrasonicenergy.

It should be appreciated that the term “pulse frequency,” as usedherein, refers to how often the ultrasound transducer generatesultrasound during a period of time.

It should be appreciated that the term “mechanical ablation,” as usedherein, refers to injuring a tissue by scratching the tissue as tocreate an abrasion in the tissue.

It should be appreciated that the term “surgeon,” as used herein,references all potential users of the disclosed ablative apparatus anddoes not limit the user of the apparatus to any particular healthcare ormedical professional or healthcare or medical professionals in general.

It should be appreciated that elements described with singular articlessuch as “a”, “an”, and/or “the” and/or otherwise described singularlymay be used in plurality. It should also be appreciated that elementsdescribed in plurality may be used singularly.

Although specific embodiments of apparatuses and methods have beenillustrated and described herein, it will be appreciated by those ofordinary skill in the art that any arrangement, combination, and/orsequence of that is calculated to achieve the same purpose may besubstituted for the specific embodiments shown. It is to be understoodthat the above description is intended to be illustrative and notrestrictive. Combinations of the above embodiments and other embodimentsas well as combinations and sequences of the above methods and othermethods of use will be apparent to individuals possessing skill in theart upon review of the present disclosure.

The scope of the claimed apparatus and methods should be determined withreference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

1. An ablative apparatus comprising: a. A guide wire containing: i. aproximal end; ii. a distal end opposite the proximal end; iii. acryogenic intake lumen originating at the proximal end of the guide wireand running substantially the length of the guide wire; and iv. acryogenic exhaust lumen running substantially the length of the guidewire, substantially parallel to the cryogenic intake lumen, andterminating at the proximal end of the guide wire; b. An ablation probesecured to the distal end of the guide wire containing: i. a proximalsurface; ii. a distal surface opposite the proximal surface; iii. atleast one radial surface extending between the proximal surface and thedistal surface; iv. at least one abrasive member on a surface of theablation probe other than the proximal surface; and v. an internaljunction into which the intake lumen and exhaust lumen of the guide wireopen; c. A transducer capable of ultrasonically driving the ablationprobe in contact with the proximal surface of the ablation probe andencircling the guide wire containing: i. at least one piezo ceramicdisc; and ii. electrodes capable of exposing the at least one piezoceramic disc to an alternating voltage; d. A handle secured at the endof the guide wire opposite the ablation probe; e. Electrical leadsrunning along the guide wire and connected to the electrodes within thetransducer; f. A catheter encasing the ablation probe, the transducer,and at least a portion of the guide wire containing: i. a proximal end;ii. a distal end opposite the proximal end; and iii. a pocket at thedistal end of the catheter encasing the ablation probe.
 2. The apparatusaccording to claim 1 further characterized by the catheter beingcomposed of a biologically compatible polymer.
 3. The apparatusaccording to claim 1 further comprising a sealed tip at the distal endof the pocket encasing the ablation probe containing one or a pluralityof slits at least partially penetrating the sealed tip.
 4. The apparatusaccording to claim 1 further characterized by the transducer containinga stack of piezo ceramic discs.
 5. The apparatus according to claim 1further characterized by the transducer containing at least one pair ofhalf cylindrical piezo ceramic discs combined to form a cylinder.
 6. Theapparatus according to claim 1 further characterized by the at least oneabrasive member on the ablation probe comprising a protrusion extendingfrom the surface of the ablation probe other than its proximal surface.7. The apparatus according to claim 1 further characterized by the atleast one abrasive member on the ablation probe comprising a thin bandon the radial surface of the ablation probe and spiraling around theablation probe.
 8. The apparatus according to claim 1 furthercharacterized by the at least one abrasive member on the ablation probecomprising a thin band on the radial surface of the ablation probe andencircling the ablation probe.
 9. The apparatus according to claim 1further characterized by the at least one abrasive member on theablation probe comprising a small particle on the surface of theablation probe other than its proximal surface.
 10. The apparatusaccording to claim 1 further comprising a cryogenic storage unit influid communication with the cryogenic intake lumen via cryogenic feedtubing attached to a proximal end of the intake lumen.
 11. The apparatusaccording to claim 1 further comprising a cryogenic retrieval unit influid communication with the cryogenic exhaust lumen via cryogenicexhaust tubing attached to a proximal end of the exhaust lumen.
 12. Theapparatus according to claim 1 further characterized by the transducerbeing capable of inducing the ablation probe to vibrate at a frequencybetween approximately 20 kHz and approximately 20 MHz.